Increase of drought stress negatively affects the sustainability of extensive sheep farming in sub-Mediterranean climate

• Increased summer drought stress affects forage properties in sub Mediterranean areas.
• Inter-annual rainfall variation influences forage features and rumen response.
• Changes in forage features will reflect in negative variations of rumen and BCS.
• Increased seasonal drought stress will present a challenge to pasture management.

The sub-Mediterranean climate, characterized by inter-annual variability, is undergoing an increase in aridity. We assessed how inter-annual variation of precipitation affects pastoral systems of central Italy, to evaluate whether climate change may cause extensive sheep farming to become unsustainable. Since the assessment of pasture-rumen interaction is considered a key tool in evaluating the status of the system, we collected data on precipitation, soil water deficit, aboveground phytomass, forage chemical composition, sheep rumen keratinization and body condition. We found that drought stress negatively affected forage quantity and quality with a pattern of responses that are partially different from those reported for both Mediterranean and Temperate regions. The most negatively affected plant communities were those of productive habitats. In clipped plots, we also observed a decrease in the re-growth capacity after clipping, especially in plant communities of southerly slopes. Positive correlations were identified for body condition with phytomass and crude protein, and negative correlations for rumen degree of keratinization with crude fibre and Acid Detergent Fibre. We suggested that the body condition of sheep deteriorates because the reduced quantity and quality of pasture changes the sheep rumen, which in turn limits absorption of volatile fatty acid.